1. Field of the Invention
The present invention relates to a structure of a vehicle seat with a lifter, which includes a pair of lifter links movable so as to enable adjustment in height of the seat, and each of such lifter links comprises a forward link member movable as a driving link member and a backward link member movable as a driven link member responsive to movement of the forward link member, and also includes a mechanism for causing movement of those lifter links.
2. Description of Prior Art
A vehicle seat with a lifter is generally of the structure wherein a pair of the lifters each comprises a forward link member and a backward link member, as stated above, and wherein the seat per se is adjustably movable in the vertical direction through operation of such lifter. As disclosed for instance from the Japanese Laid-Open Publication No. 2001-88589, the seat is connected, via the forward and backward link members, with securing members fixed on a floor of vehicle, such as securing brackets or the like, so as to be supported thereon.
In this connection, in general, seat belts are provided on the vehicle seat, such that each of them may be drawn outwardly from a retractor mounted on a vehicle body in order to restrain a seat occupant to the seat. In such an emergency case as a collision, an excessive great load is applied from the seat occupant to the seat belt, and most of the load is directly escaped via the seat belt to the vehicle body. Therefore, even in the case of the above-stated seat with lifter, such excessive great load applied thereto is smoothly transmitted through the link members of the lifter to the vehicle body, without giving serious damage to the lifter.
But, there is known a vehicle seat structure wherein a seat belt is retractably mounted and not connected with the side of vehicle seat. This kind of seat is the so-called “a vehicle seat with built-in seat belt arrangement” having a retractor of the seat belt provided within the seat, which is for example disclosed from the Japanese Laid-Open Publication No. 2002-59770.
In contrast to a normal seat of the type having seat belts directly connected with the vehicle body, the vehicle seat with built-in seat belt arrangement has been with such a problem that a great load applied from a seat occupant to the seat belt is directly inputted to and exerted on the seat per se, as a result of which, support and connecting elements for supportively connecting the seat with a securing member fixed on the vehicle floor require a high strength sufficient to withstand the great load inputted from the seat belt.
On the other hand, it is possible to combine such vehicle seat with built-in seat belt arrangement with the aforementioned vehicle seat with lifter so as to provide a vehicle seat with lifter and built-in seat belt which is improved in user-friendly and easy-to-use aspects. But, considering the afore-stated excessive great load, such new type of vehicle seat requires a strength enough to withstand that great load, and in particular, the excessive great load applied from the seat belt is directly exerted upon the forward and backward link elements which will be damaged or bent. Of course, one can contemplate on increasing the thickness of securing members provided on the seat and vehicle floor as well as the thickness of the link elements of the lifter, and further increasing the diameter of connecting pins among those members and elements. However, such reinforcement result in increase of the weight of whole of seat, a corresponding increase of costs involved, and complicated structure of the seat.